How to create a flower unfurling effect?
Create a flower petal, use the object instancer node to duplicate it and connect it to a for loop. 

The key concept will be the following: Connect a Time Info into Animate Number nodes. Use this value to drive the Rotation and the Scale to make the petals flip open and "grow".
Now all object will flip open at the same time. To make them open one after each other, qdd the instance number to the Time Info.

The rest is just getting the proper timing, spacing and interpolation. 

This node setup should get you started.